Proton-sensing G protein-coupled receptors as regulators of cell proliferation and migration during tumor growth and wound healing.

Dysregulation of pH is a feature of both tumor growth and tissue repair. In tumors, microenvironmental changes, like in lactate metabolism, lead to altered intra- and extracellular pH (pHi , pHe ) and vice versa. In wounds, barrier disruption results in extensive variations in pHe on the wound surface. It is known that altered extracellular proton concentrations have a major impact on cell turnover and migration as well as on the metabolic activity of cells involved in tumor spread and wound closure. The proton-sensing G protein-coupled receptors (GPCRs) GPR4, GPR65 (TDAG8), GPR68 (OGR1) and GPR132 (G2A) are activated via a decrease in pHe and transduce this signal to molecular intracellular pathways. Based on the current knowledge, we speculate on the role of proton-sensing GPCRs in wound healing and on their potential as mechanistic linkers of tumor growth and tissue repair.

NHE1 expression at wound margins increases time-dependently during physiological healing.

Wound repair is an orchestrated process, encompassing the phases of inflammation, proliferation and tissue remodeling. In this context, sodium hydrogen exchanger 1 (NHE1) is crucial to epidermal barrier integrity and acidification. Recently, we found that extracellular pH (pHe) on wound surfaces is dramatically increased initially after barrier disruption, and that pHe decreases gradually during physiological healing. Additionally, we have shown that spatial NHE1-patterns account for pHe-gradients on surfaces of chronic wounds. Here, we show that NHE1-expression is very low at margins initially after wounding and that it increases massively during the time-course of physiolgical healing. This finding is in accordance with the decrease of pHe on wound surfaces, which we reported on in previous works. Thus, we show that NHE1 is an interesting target when it comes to modification of surface pHe on wounds, both acute and chronic, and that NHE1 is time-dependently regulated in physiological healing.

Nodular Cutaneous Amyloidosis Resembling a Giant Tumor.

A 79-year-old man presented with a large tumor on the left side of his head, which had grown over 5 years. Regional lymph nodes were impalpable and computed tomography revealed no signs of bone infiltration. Histology showed that the entire dermis was filled with amorphous eosinophilic material. Immunohistochemistry was negative for cytokeratin, but showed that the dermis and parts of the subcutis were filled with amyloid consisting of immunoglobulin light chains. There were no signs of paraproteinemia or underlying plasmocytoma. In electron microscopy, the typical amyloid fibrils were found. The tumor was completely removed via curettage. At 1-year follow-up, the patient was doing fine with no signs of relapse or systemic disease.

Fusion of CCL21 non-migratory active breast epithelial and breast cancer cells give rise to CCL21 migratory active tumor hybrid cell lines.

The biological phenomenon of cell fusion has been linked to tumor progression because several data provided evidence that fusion of tumor cells and normal cells gave rise to hybrid cell lines exhibiting novel properties, such as increased metastatogenic capacity and an enhanced drug resistance. Here we investigated M13HS hybrid cell lines, derived from spontaneous fusion events between M13SV1-EGFP-Neo breast epithelial cells exhibiting stem cell characteristics and HS578T-Hyg breast cancer cells, concerning CCL21/CCR7 signaling. Western Blot analysis showed that all cell lines varied in their CCR7 expression levels as well as differed in the induction and kinetics of CCR7 specific signal transduction cascades. Flow cytometry-based calcium measurements revealed that a CCL21 induced calcium influx was solely detected in M13HS hybrid cell lines. Cell migration demonstrated that only M13HS hybrid cell lines, but not parental derivatives, responded to CCL21 stimulation with an increased migratory activity. Knockdown of CCR7 expression by siRNA completely abrogated the CCL21 induced migration of hybrid cell lines indicating the necessity of CCL21/CCR7 signaling. Because the CCL21/CCR7 axis has been linked to metastatic spreading of breast cancer to lymph nodes we conclude from our data that cell fusion could be a mechanism explaining the origin of metastatic cancer (hybrid) cells.

Characterization of hybrid cells derived from spontaneous fusion events between breast epithelial cells exhibiting stem-like characteristics and breast cancer cells.

Several data of the past years clearly indicated that the fusion of tumor cells and tumor cells or tumor cells and normal cells can give rise to hybrids cells exhibited novel properties such as an increased malignancy, drug resistance, or resistance to apoptosis. In the present study we characterized hybrid cells derived from spontaneous fusion events between the breast epithelial cell line M13SV1-EGFP-Neo and two breast cancer cell lines: HS578T-Hyg and MDA-MB-435-Hyg. Short-tandem-repeat analysis revealed an overlap of parental alleles in all hybrid cells indicating that hybrid cells originated from real cell fusion events. RealTime-PCR-array gene expression data provided evidence that each hybrid cell clone exhibited a unique gene expression pattern, resulting in a specific resistance of hybrid clones towards chemotherapeutic drugs, such as doxorubicin and paclitaxel, as well as a specific migratory behavior of hybrid clones towards EGF. For instance, M13MDA435-4 hybrids showed a marked resistance towards etoposide, doxorubicin and paclitaxel, whereas hybrid clones M13MDA-435-1 and -2 were only resistant towards etoposide. Likewise, all investigated M13MDA435 hybrids responded to EGF with an increased migratory activity, whereas the migration of parental MDA-MB-435-Hyg cells was blocked by EGF, suggesting that M13MDA435 hybrids may have acquired a new motility pathway. Similar findings have been obtained for M13HS hybrids. We conclude from our data that they further support the hypothesis that cell fusion could give rise to drug resistant and migratory active tumor (hybrid) cells in cancer.